Math & spatial-temporal reasoning
The same thinking a child uses to picture how shapes fit together is the thinking that music practice exercises every day.
Some of the earliest and most cited work in this area comes from psychologist Frances Rauscher and physicist Gordon Shaw. In a 1997 study published in Neurological Research, preschool children who received piano keyboard lessons showed lasting improvement in spatial-temporal reasoning — the ability to think ahead and picture how parts fit together over time.
Later reviews have continued to explore links between sustained music instruction and mathematical thinking. The strongest, most consistent finding is qualitative and encouraging: children who study an instrument tend to strengthen exactly the kind of ordered, sequential reasoning that mathematics rewards.
Source: Rauscher, F. H. & Shaw, G. L. et al. (1997), Neurological Research.